The invention relates to a device for transferring a material in the form of a film applied to a carrier strip onto a substrate, such as a sheet of writing or drawing paper, comprising a housing in which a supply reel for the film-coated carrier strip and an empty reel for receiving the de-coated carrier strip are arranged, wherein the film-coated carrier strip is guided over an applicator foot provided at least in the region which is looped around by the carrier strip with a clip-type slide element of a friction-reducing material secured to the applicator foot.
Hand devices of that kind for transferring a film (for example, adhesive strip, concealing substance, marking ink, etc.) are known. In that case, in order to achieve a smooth motion and good capability of transfer of the film onto the substrate various embodiments for the shapes of the applicator foot are known. Thus, the applicator foot can be equipped with, for example, an applicator roller which preferably has a rubber-elastic running surface. However, as the external diameter of a functionally effective applicator roller cannot be kept as small as desired, because a good adaptation to the substrate requires a minimum thickness for the elastic running ring and the rotational mobility presupposes a sufficient difference between axle stub and external diameter, such an applicator roller has disadvantages. Accordingly, in most solutions the applicator foot usually has an applicator strip which has advantages relative to an applicator roller, as a sharper angling of the carrier strip is possible in the transfer phase, whereby the torn-off piece has less tendency to formation of a wavy edge after completion of the transfer. Thereagainst it is disadvantageous relative to the applicator roller solution that in the case of the applicator strip the carrier strip is guided thereover with a friction couple which, in dependence on the respective carrier strip quality, can lead to undesired heavygoing.
In principle, synthetic materials which have a good sliding property are known, for example polytetrafluorethylenes (PTFE), but which are higher in cost by a multiple than the standard materials usually used for the components of a device of the kind in question. Accordingly, the use of an applicator foot of polytetrafluorethylene is excluded on cost grounds.
As polytetrafluorethylene is not a true thermoplastic, a loading of the region, which is effective with respect to guidance, of the applicator foot by this high-quality material in a multi-component injection-moulding process or a subsequent injection-moulding process has to be excluded. A conceivable solution, such as gluing the applicator strip by a self-adhesive foil coated with fluoroplastics, has in fact been attempted already, but from the viewpoint of production engineering is unsuitable for mass-produced articles.
A device of the category in question is known from U.S. Pat. No. 5,430,904. In this device the applicator foot is provided in the region which is looped around by the carrier strip with a slide element made of a friction-reducing, rubber-elastic material and fastened to the applicator foot. This slide element is to improve the transfer of the film onto the substrate. In the active pressing segment of the applicator strip it has a rotationally symmetrical curved profile and as an inevitable result thereof a small linear contact region with the substrate. It has proved that on transfer of the adhesive layer onto a substrate the adhesive layer easily tears, so that the carrier strip slides over the substrate on a silicon layer and the drive is interrupted.
It is accordingly the object of the invention to so improve a device according to the category that a faultless transfer of the film onto the substrate is guaranteed in return for smallest possible outlay.
In accordance with the invention this object is met in the case of a device of the kind denoted in the introduction in that the slide element has an elliptical cross-sectional shape in such a manner that on transfer of the film onto the substrate the contact pressure region of the slide element bears over an area against the substrate with interposition of the carrier strip.
According to the invention it is possible in an unexpectedly simple manner to create, by simple change in the cross-sectional shape of the slide element, a substantially larger contact area between the slide element on the one hand and the substrate on the other hand so as to make available a sufficient contact pressure area, which ensures that the adhesive material layer does not tear off so that a faultless functioning of the device is given. The slide element itself can in this construction nevertheless be decidedly small, for example it can be produced as a semi-finished product of the smallest dimensions (for example, with an external diameter of 1 to 1.2 millimeters and 0.2 to 0.3 millimeters wall thickness), in that it is cut off to the desired length, slit in longitudinal direction and then spread apart and pushed onto the applicator foot. This can be carried out automatically in simple manner.
With particular advantage it is proposed in that case that the slide element consists of polytetrafluorethylene (PTFE) as this material has a particularly good sliding property. Obviously also materials with comparable characteristics can be used.
Moreover, it is proposed with advantage that the end portion, which receives the slide element, of the applicator foot similarly has a cross-sectional shape which is elliptical at least regionally. The slide element can then be produced in particularly simple manner as the internal profile thereof can largely correspond with the external profile. It is then, in addition, securely held at the applicator foot.